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Oregon spotted frog released into the wild to halt population crash

23/09/2008 12:06:50

Oregon spotted frog. Washington Department of Fish and Wildlife

In an effort to re-establish their populations in Washington State, approximately 500 Oregon spotted frogs were released into the wild after spending the first seven months of their lives in a captive rearing program.

September 2008. Biologists from the Washington Department of Fish and Wildlife (WDFW) and the U.S. Army released the frogs into Dailman Lake on the Fort Lewis Military Reservation in Pierce County in a collaborative effort to return the state-endangered frog to a portion of its historic habitat.

Tiny frogs
The frogs, which weigh less than an ounce and are marked with a nontoxic dye, were collected as eggs in March and nurtured in captivity at Northwest Trek Wildlife Park to improve their chance of survival once they return to the wild.
"This is the first-ever captive rearing and release program for the Oregon spotted frog in Washington and represents a significant first step in our joint effort to help recover this fragile species," said Harriet Allen, WDFW endangered species program manager.

The captive-rearing strategy, called "head starting" is based on the premise that juvenile frogs are thought to be less vulnerable and better able to survive when released back into nature, Allen said. "Also, previous studies in British Columbia show that releasing large numbers at the same time has been the most successful approach," she said.

The Oregon spotted frog - devastated by habitat loss, predation and disease
The Oregon spotted frog historically ranged from south-western British Columbia to north-eastern California. The frog is now believed to have disappeared from California and Oregon's Willamette Valley and has suffered significant declines elsewhere in its historic range. Loss of habitat, predation by non-native species such as the American bullfrog, and disease have decimated its numbers, which prompted listing it as a Washington state-endangered species in 1997.

Dailman Lake
Through a partnership with the Fort Lewis Fish and Wildlife Program, the Dailman Lake area was chosen for reintroduction because it contains diverse wetlands connected to a stream system capable of supporting and sustaining a frog population, said Jim Lynch, wildlife biologist at Fort Lewis.

As a first step in the project, biologists collected fertilized eggs last spring from breeding areas in Klickitat and Thurston counties, which are the only known areas with existing populations within the frog's historic range in Washington. They were then transported to Northwest Trek Wildlife Park and Oregon Zoo for rearing and monitoring. Frogs reared at the Oregon Zoo will be released at the site at a later date.

The goal of the reintroduction program is to establish a self-sustaining population of Oregon spotted frogs at Fort Lewis and set the stage for a structured recovery effort that will continue for several years, Lynch said.

The reintroduction program was first developed in 2007 through a collaborative effort by WDFW, Fort Lewis, Northwest Trek Wildlife Park, Point Defiance Zoo & Aquarium, Oregon Zoo, Washington State Department of Transportation, U.S. Fish and Wildlife Service, Woodland Park Zoo, Port Blakely Tree Farms, Washington Department of Natural Resources, NW Zoo & Aquarium Alliance, U.S Geological Survey, Mountain View Conservation & Breeding Centre and The Nature Conservancy.

The project's start-up coincides with efforts by the Association of Zoos & Aquariums, which is highlighting 2008 as the Year of the Frog to mark a major conservation effort to address global amphibian extinction, Lynch said.

"Frogs are found in all parts of the world and are known as sentinel animals by alerting us to serious environmental and climate changes that can affect all species," Lynch said. "They also play an important role in balancing ecosystems and when they disappear from their habitat, that ecosystem is disrupted."

Activities related to the reintroduction program are being funded through grants from the Point Defiance Zoo & Aquarium and the Association of Zoo & Aquarium's amphibian fund.


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